The ultimatum was issued on Thursday night at the close of the second day of a strike that is costing the airline 500, 000 dollars (394,000 euros) a day, the state-run Herald newspaper reported.

"The board and management have resolved to give them a 24-hour notice to go back to work," Jonathan Kadzura, board chairman of Air Zimbabwe, was quoted as saying in the Herald.

"It must be understood clearly that the industrial action is illegal and if they do not go back to work inside the 24 hours, legal and disciplinary action will be taken," Kadzura said.

"Government does not have any money," he added.

Air Zimbabwe says it cannot afford to pay the 60 pilots their full salaries of 2, 500 dollars a month, but has promised to make up their back-wages.

Pilots are supposed to receive up to 10, 000 dollars a month including allowances, the Herald reported on Thursday.

There was chaos at Harare International Airport as the strike began on Wednesday, with two planes left abandoned on the runway and disgruntled passengers milling around the airport.

The strike led to the cancellation of all Air Zimbabwe flights, including those to Britain, South Africa and Zambia.

Air Zimbabwe is one of several state-owned firms that are posting losses and have been shortlisted for a sell-off. The airline is weighed down by debt, an ageing fleet and high staff turnover.

The strike has left some passengers stranded at the country's airports, while hoteliers and tour operators in the resort town of Victoria Falls have been forced to cancel bookings.